You wont be able to enforce every arbitrary agreement. The constitutional courts will only rule on limited matters such as physical aggressions.

And (for example) for Oracle to enforce non-compete, It will have to come in agreement with big corps such as Google/Amazon/Facebook/etc. This will work for most cases. But former-employee of Oracle will be able to work at Joyent.

In conclusion, You have to get help from others to enforce an agreement not enforced by Govt.

Also note, constitution ~= what everyone consents on. That is, 1. It will be short & sweet. Everyone will be able to understand it. No suprises. 2. It will never have surveillance measures.